This invention relates generally to the use of reconstituted tobacco sheet as a filler material to be used in admixture with leaf tobacco in smoking materials such as cigarettes and cigars. This invention relates particularly to a method of improving the property known as filling power. This invention also relates to making tobacco products for other uses which after shredding have superior shred length and shred resiliency.
Cigarette filler is produced by cutting tobacco leaf or reconstituted tobacco sheet into shreds or pieces about 0.03 inches or less wide and of varying length, typically averaging 8 mm or longer. These shreds are packed into a cigarette under controlled compressive forces. The specific volume of the cigarette filler, measured at a controlled moisture content of about 13%, indicates the filling power.
In the production of cigar filler a machine is used to thresh the sheet into smaller fragments of irregular dimensions and with an average size similar to about 10 mm square. Such fragments of cigar filler are incorporated into the cigars without the subsequent cutting into narrow shreds as used in cigarette filler.
Chewing tobacco and snuff are examples of non-smoking tobacco products which can be sold as shredded products and which benefit from improvements in the length and resiliency of the resulting shreds.
Reconstituted tobacco sheet, conventionally is produced by the so-called band processes or by the paper machine process. The band processes involve applying a dispersion of tobacco particles, in combination with other additives and adhesives, to a metal carrier belt where the dispersion is dried and it thereby becomes a sheet which is peeled off the belt. The typical thickness of such a dried sheet is 0.006 to 0.008 inches. Such band processes are well known and have been described by Jansson and Lilja in U.S. Pat. No. 3,162,200, by Pihl in U.S. Pat. No. 2,971,517, by Gretz in U.S. Pat. Nos. 3,590,493 and 3,589,032, by Egri in U.S. Pat. Nos. 3,894,544 and 4,069,831, by Schmidt and Hoge in U.S. Pat. No. 4,306,578, and by Schmidt in U.S. Pat. No. 4,325,391.
The tobacco sheet can also be produced on a paper machine where water is drained from a fibrous slurry of tobacco particles, and the web or sheet may be subsequently treated with additives and dried. Such paper machine processes have been described by Selke in U.S. Pat. Nos. 3,860,012 and 4,182,349, and by Arledter and Marek in U.S. Pat. No. 3,870,054.
There have been various efforts to improve the filling power of tobacco sheet. A process for the non-uniform compacting of tobacco sheet by a specialized belt treatment was described by Licis in U.S. Pat. No. 3,431,915. Schweitzer in U.S. Pat. No. 3,430,634 described a process for creping a tobacco sheet by applying the moist tobacco sheet to a creping roll and doctoring it from the creping roll. Cogbill in U.S. Pat. No. 4,258,728 described a process which involves simultaneous steaming, wrinkling and shattering of tobacco sheet to improve filling power. Other processes for increasing the filling power of tobacco sheet have incorporated air or foam-generating agents in the wet sheet for the purpose of achieving a final structure of lower density and higher specific volume.
Laminations of two layers of tobacco sheets have been used heretofore to create visual effects such as to simulate the vein structure of natural tobacco leaf in cigar wrappers, and this was described by Godfrey et al in U.S. Pat. No. 4,109,665 and by Sinclair et al in U.S. Pat. No. 4,135,962. Conventional laminations where two or more plies of reconstituted tobacco sheet are continuously and intimately connected have not found advantage to produce a cigarette or cigar filler having improved filling power.
Reconstituted tobacco sheet made by one of the band processes always tends to have one particularly smooth surface, which results from the smoothness of the metal belt on which it was formed. The smooth surface has certain disadvantages. The smooth surface can cause chopped pieces to experience slippage on inclined belt conveyors. Also, if the moisture content of a band-formed tobacco sheet exceeds about 18% or more, and if the 5 cm cut squares of tobacco sheet are randomly pressed together, such as in the bottom of large bulk shipping containers, there is a tendency for the pieces to form larger clumps of irregularly cohering pieces, with such clumps often containing ten or more individual plies. Such thick clumps, when passing through the shredding machine, result in thicker shreds, which resemble miniature logs, and such shreds have lower specific volume and lower filling power.
Tobacco sheet made by the paper machine process can also form unwanted laminations. Such unwanted sheet structure generally is brought about by a high localized surface concentration of tobacco extractives which are reintroduced into the tobacco sheet after the fibrous web has been formed.
The ideal reconstituted tobacco sheet would be visually indistinguishable from leaf tobacco. However, most sheet products are very two-sided and therefore readily identifiable. This effect is more pronounced with band-formed sheet than with sheet made by the paper machine process.